Activation of human umbilical vein endothelial cell progelatinase A by phorbol myristate acetate: a protein kinase C-dependent mechanism involving a membrane-type matrix metalloproteinase.

Matrix metalloproteinases play an important role in tumor invasion, angiogenesis and inflammatory tissue destruction. The 72-kd gelatinase A is the most widely distributed. Along with the 92-kd gelatinase B, it plays an important role in basement membrane turnover. Gelatinase A is secreted as progelatinase A and, when activated, can cause extracellular matrix destruction. The physiologic mechanism of this activation is not well understood. Based on the importance of endothelial cells in inflammation and cancer, we sought in this study to systematically study the PMA-induced activation of endothelial cell progelatinase A. Using HUVEC, we demonstrated that PMA-induced activation of progelatinase A in these vascular endothelial cells (a) was protein kinase C-dependent as it was blocked by H-7; (b) occurred through cell-mediated events as PMA was unable to activate progelatinase A in a cell-free system and that low dose tissue inhibitor of metalloproteinases-2, but not tissue inhibitor of metalloproteinases-1, totally inhibited PMA-induced activation; (c) was accompanied by an increase in the membrane-type matrix metalloproteinase (MT-MMP). We also found that the combination of PMA and the cytokine tumor necrosis factor-alpha increased HUVEC secretion and activation of gelatinase B. In conclusion, our data show that PMA activation of vascular endothelial cell progelatinase A is a cell membrane event that is at least partially mediated through a PKC-dependent mechanism and is accompanied by an increase synthesis of MT-MMP. These data suggest a role for MT-MMP in the activation of progelatinase A in vascular endothelial cells.